People are encouraged to do exercise because exercise may make metabolism proceed smoothly to remove a risk factor for adult diseases. A considerable number of medical reports have been published on the effect of exercise as a means for rehabilitation of patients of myocardial infarction. On the other hand, various diseases and complications resulted from doing sports are problems in sports medicine, including `athletic anemia` and `sudden death`.
Causes of athletic anemia may include insufficient red blood cell production due to accelerated protein metabolism during exercise and/or insufficient iron intake, hemolysis by chemical substances such as lactic acid produced during exercise, and hemolysis by physical actions such as impulse during exercise.
Many of the cases of sudden death have chronic underlying diseases, though some of the cases seem morphologically to have no underlying disease where definite diagnosis is often very difficult. Many cases of sudden death during sports have been reported; sudden death occurs most frequently during running sports such as running, jogging, and marathon, and frequently during playing basketball, baseball, and swimming.
Cases of sudden death may be classified into two groups; one group with latent organic underlying diseases, and one group with mild organic underlying diseases or without remarkable organic change. Cases of the former group rarely become problematic because they have subjective symptoms and some of them are under medical treatment. However cases of the latter group may become problematic and may frequently give rise to public discussion because they have no subjective symptoms, are judged to have no abnormality in medical examination, but die suddenly as a result of action such as doing sports. Cases of acute heart failure of unknown cause in the young (so-called a disease causing sudden death) belong to the latter group, and frequently give rise to public discussion in relation with the excessive exercise or rigorous training.
The nature of acute heart failure in the young still remains unknown and there are various views on the nature. Generally a seemingly healthy and robust young man (Acute heart failure occurs mostly in men.) falls down abruptly with a groan to die suddenly. Autopsy of such a man reveals mild cardiac hypertrophy accompanying enlargement of the heart, thinning and narrowing of vessels including coronary artery and aorta, and other findings, though arteriosclerosis is rarely found. The possibility that sudden death may follow arrythmia during or after exercise should be taken into account.
It has been clarified that EPA and DHA have physiological actions including decrease of neutral lipid and total cholesterol in blood, increase of HDL cholesterol, reduction of platelet aggregation, reduction of blood viscosity, and elevation of fragility of red blood cells. These actions make blood flow fluently and aggregate with difficulty. DHA, being rich in the tissue of the brain cell membrane, has been expected to have some influence on the function related to the nerve tissue, such as learning function, and is being studied actively.
Sawaki et al.(Juntendo University) noticed that the Norwegian athletes who obtained good results in the Lillehammer Winter Olympic Game had taken DHA and EPA as auxiliary nutritious foods, and studied the influence of intake of DHA and EPA on the training effect in the track and field athletes. The study showed that there is a great difference between those who took DHA/EPA and those who did not, and it was assumed that intake of DHA/EPA may enhance the oxygen-transporting ability to capillaries.
Studies on the influence of such fatty acids on exercise capacity will be made more actively in future, and development of practical techniques supported by the results of studies is awaited. The relationship between the reduced fragility of red blood cells and hardened membrane of red blood cells has been reported in several diseases, and increased fluidity of the red blood cell membrane may make red blood cells fragile. Based on these findings, agents to remove risk factors during exercise are being expected to be developed in the field of prophylaxis and medical care.